This invention relates to a fuel line heating system and more particularly to a heating system for preheating the fuel in an outlet conduit located in the fuel storage tank.
In cooler climates, diesel engine operation has encountered a problem attributable to the formation of wax crystals, due to the parathon content of the fuel. For reasons of economy, No. 2 fuel oil is desired, but this grade is afflicted with the wax problem, which can be so sever in extremely cold temperatures as to clog the fuel line and starve the engine of fuel. To avoid this problem, No. 1 fuel (kerosene) has been recommended, but the incremental cost per gallon is prohibitive. The other solution to the problem is to provide a system for heating the fuel.
Systems such as shown in the Blitz '551 and '891 patents attempt to heat the entire fuel tank in order to prevent the waxing problem, while other systems such as that shown in the Gorans '851 patent regulate the temperature of the fuel after it has left the fuel tank. Systems such as these have inherent problems in that the Blitz systems must use a rather substantial size coil in order to heat the entire fuel tank while the Gorans system does not account for the waxing that occurs in the tank adjacent the outlet.
Other patents such as the Davis '996 patent teach the use of a separate chamber in the tank for heating and filtering the fuel and the Allen '776 patent utilizes a system that constantly circulates the fuel even when the engine is not running in order to het it.
In accordance with one aspect of the invention the in tank fuel line heating system is provided with a fuel outlet conduit that extends downwardly into the tank to a point substantially near the bottom of the tank. A coolant circulating circuit that circulates the heated engine coolant is located adjacent the fuel outlet conduit and serves to transfer heat from the engine heated coolant to the fuel in the fuel outlet conduit.
In accordance with another aspect of the invention, a fuel return conduit is provided for returning unused fuel from the engine to the tank. This conduit is located adjacent the fuel outlet conduit and extends downwardly into a tank to a point just above the inner most end of the fuel outlet conduit.
In accordance with yet another aspect of the invention, the coolant circulating conduit is provided with a portion that extends parallel to the bottom of the tank and serves to heat that area of the tank and prevent the formation of ice from any water condensate that may have formed in that portion of the tank.
The present invention thus provides a compact system that does not occupy a great deal of space in the tank and a system that will preheat the fuel as it leaves the tank through the fuel outlet conduit. Any wax buildup in the tank is thus eliminated as it is heated in the fuel tank outlet.